Turbulent diffusion in the core of a pipe with uniform transverse flow at the walls

Abstract

AbstractAn analysis of point source turbulent diffusion of a gaseous tracer in the core of a circular straight porous pipe with uniform transverse flow at the walls is presented. Time averaged concentration distributions were measured at four distances downstream from a point source located at the axis of a fully developed turbulent flow of air in a 6‐in. pipe. Experiments were run at average velocities between 4.36 and 23.0 ft./sec. (corresponding to Reynolds numbers 12,000 to 66,000) with injection velocities ranging from 0 to 0.170 ft./sec. and suction velocities from 0 to 0.048 ft./sec. The highest injection rate corresponded to 58% by volume of the main stream. Good agreement is obtained between the expeimental and the calculated concentration profiles.The present study shows that the plume width of the disperising tracer is considerably affected by the transverse flow. It also shows that the eddy diffusivity in the pipe core and the radial mass flux increase with fluid injection and decrease with suction through the pipe walls. Also, for increasing values of aspect ratio, they increase in the case of injection and decrease in the case of fluid suction.